1. Technical Field
The present invention generally relates to a solid composition for treating water, e.g., swimming pools, hot tubs, spas, toilets, etc.
2. Description of the Related Art
In order to insure that the water in, for example, a pool or spa, is safe, it must be properly sanitized to prevent any health problems arising due to such contaminants as, for example, algae, bacteria, or any other pathogens which may be in the water. Thus, it is the goal of any owner or operator of recreational water bodies, swimming pools, spas, hot tubs or the like to provide water which is safe and properly sanitized. To this end, the owner or operator may choose from a wide variety of biocidal chemical systems to ensure that a biocidally effective amount of a water-treating agent is present in the water body on a continuous basis.
The more commonly used biocidal agents are halogen-containing biocides. The halogen is typically chlorine and can be in a number of different forms, e.g., chlorine gas, alkali metal hypochlorites, alkaline earth metal hypochlorites, halogenated hydantoins and chlorinated isocyanuric acid analogues. Representative examples of such halogen-containing biocides include sodium hypochlorite (liquid bleach), calcium hypochlorite, lithium hypochlorite, chlorinated isocyanurates, etc. When any of these materials interact with water, they undergo hydrolysis to form free chlorine consisting predominantly of hypochlorous acid (HOCl), which is the sanitizing agent, and hypochlorite ion.
Chloroisocyanuric acids (also known as chloroisocyanurates) are stabilized organic chlorine compounds. Examples of such chlorine compounds are sodium or potassium dichloro-s-triazinetrione (commonly known as dichloro) and trichloro-s-triazintrione (commonly known as trichlor, or TCCA). Both dichlor and trichlor are used for treating water bodies. When rapid chlorine delivery is desired, dichlor is commonly used due to its greater solubility whereas trichlor is commonly used when a slow and sustained release of chlorine delivery is desired for a longer period of time due to its lower solubility. Generally, trichlor is compressed into a tablet form for ease of application and use which further slows and prolongs the release of chlorine to the water source.
It is common practice to blend other performance enhancing chemicals with the halogen-containing biocides to provide multifunctionality to the compositions which is highly desirable for use in water treatment applications. Examples of such performance enhancing chemicals include algicides, algistats, flocculants, scale inhibitors, water softeners, dissolution control aids, chelants, tabletting aids, binders, colorants, and fragrances.
It is well known to combine a boron source material such as boric acid or borax with trichlor along with other additives such as a non-halogen oxygen donor material or glycoluril. See, e.g., U.S. Pat. Nos. 5,478,482; 5,514,287 and 5,670,059. The addition of a boron source to a chlorine source such as trichlor has typically been used by the industry for the purpose of providing algistatic properties in addition to lowering the cost of the composition. However, one problem associated with this combination is that the compressed solid composition has a propensity to dissolve at a faster rate than trichlor itself. See, e.g., U.S. Pat. No. 5,648,314. This rapid dissolution of the chlorine source such as trichlor is generally undesirable and inconvenient since users are then required to add the compositions more frequently to maintain the desired level of residual chlorine in the water. Another problem associated with this combination is that boron sources are known to promote the chlorine off-gassing in a trichlor formulation.
Trichlor is also known to be formulated with dissolution aids to increase the speed of dissolution. Examples of such dissolution aids include salts such as alkali metal and alkaline earth metal carbonate salts, including sodium carbonate, sodium bicarbonate, potassium carbonate and calcium carbonate as disclosed in U.S. Pat. No. 4,389,318. U.S. Pat. No. 6,426,317 teaches the use of alkali metal salt of 1,3,5-triazine-2,4,6-triones as a dissolution accelerant for trichlor.
Another performance enhancing additive that is commonly added to a trichlor composition is polyphosphates. It is also well known that the addition of a polyphosphate softens the water and helps minimize the scale build up on pipes and heat exchangers. See, e.g., U.S. Pat. No. 3,488,420.
However, there are drawbacks to using many of these additives. Most of these functional additives are highly water soluble and tend to make such trichlor compressed solid compositions dissolve faster than that made from trichlor alone. Trichlor products also give off chlorine gas and in combination with some of these additives also impart chemical instability in the final formulation which is of concern for sale on a commercial level.
A need therefore exists for improved solid water treatment compositions containing a halogen-containing source such as a chlorine source for treatment of water without affecting dissolution while reducing halogen off-gassing, e.g., chlorine off-gassing.